Speakers used as car-door mounted speakers or the like are required to have waterproof property to such an extent as to prevent water intrusion into the inside of a vibration plate since there is a likelihood that rain water, a shampoo solution for car-wash or the like is splashed thereon when a door is opened or closed or a window is opened or closed during rain or car wash.
A mainly used method of manufacturing speakers having such waterproof property is a dipping method that includes forming paper pulp, which is suspended in an aqueous solution, into paper, molding it into a plate, and dipping it in a working fluid made of an organic solvent with a fluorinated resin dissolved therein.
However, the dipping method is required to separately carry out a step in which a subject is to be treated with oil, in addition to a paper-making step in which a subject is to be treated with water, which causes a problem of necessitating troublesome manufacturing procedures, as well as a problem of causing an environmental pollution or the like due to the use of the organic solvent for dissolving the fluorinated resin.
Furthermore, speakers as manufactured have a problem of providing only insufficient waterproof performance to a shampoo solution for car wash.
Patent Document 1 proposes a method of making paper by the use of paper pulp with an aqueous synthetic resin fixed thereto, which resin having a fluorine group at an end.
However, the problem of providing only insufficient waterproof performance to a shampoo solution for car wash has not yet been solved.
Therefore, there is a demand for speakers that can be easily manufactured, causing less environmental pollution, and exhibits satisfactory waterproof performance to a shampoo solution for car wash.
Patent Document 1: Official Gazette of Japanese Patent Application Laid-open No. Hei-5-183985